The long term goal of this continuing work is to quantitatively characterize skeletal muscle structure and function noninvasively with nondestructive imaging modalities, and to implement robust methods for diagnosing disease and improving clinical management. In particular, we seek to develop novel insights into skeletal muscle pathophysiology based on unique information available from the interaction of ultrasound with soft tissues. Heretofore we have focused on cardiac remodeling in myocardial infarction and idiopathic cardiomyopathy, and on physiologic and pathologic vascular structure and function. We now propose to extend the knowledge gained from these efforts in order to quantitatively "phenotype" the remodeling process in genetic disorders of skeletal muscle as a consequence of dystrophin deficiency in animal models. The ultimate goal is to produce a comprehensive package for quantitative ultrasound tissue characterization of muscular dystrophy, which is fully validated by robust independent measures (e.g., strength testing)